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The active components of a rechargeable lithium ion battery in the charged state consist of lithium cobalt dioxide in the positive electrode and graphite in the negative electrode. LiIon cells attain, when fully charged, a voltage of approximately 4.2 V. Due to the electrolysis of water (decomposition into oxygen and hydrogen) which then sets in, no aqueous electrolyte may be used.
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The conductance of the electrolyte is not as good as in the case of NiCd/NiMH cells. For this reason organic solvents and conducting salts are used. These have a higher internal resistance and are less well suited for high discharge currents. Moreover, the current output within the low temperature range is much restricted.
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Moreover, in the case of LiIon systems electronic safety shutdown circuits are required as well as more involved charging systems. Here the costs compared to NiCd/NiMH cells are not negligible.
The advantage is the higher energy density with respect to volume and weight. Due to the higher voltage, a single LiIon cell can replace three NiCd/NIMH cells.
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